The short answer
Magnesium-containing antacids should be kept at least 2 hours before or after oral ofloxacin, following its current label. A small human study of a combined magnesium/aluminum antacid supports separating doses, but it did not test simultaneous administration or isolate the effect of magnesium alone.
What this answer covers
Oral ofloxacin tablets with magnesium-containing antacids. Direct study used a combined magnesium/aluminum hydroxide preparation; eye and ear drops are outside this absorption finding.
- Supplement or preparation
- Magnesium
- Medication ingredient
- ofloxacin
What did the original experiment find?
Sixteen participants received ofloxacin 400 mg with a magnesium/aluminum hydroxide antacid at different separated times. Antacid two hours before the antibiotic produced a small reduction in overall exposure and the peak concentration. The investigators considered changes generally not clinically important when products were at least two hours apart. Taking both at the same moment was not tested.
What timing should I use?
Current ofloxacin tablet directions use at least 2 hours in either direction. This remains the product instruction even though a small exposure change was measurable with antacid two hours before the dose. Have the pharmacist coordinate frequent antacid use with the prescription. The study cannot be used to shorten the interval to simultaneous dosing.
How closely does the evidence match my product?
A magnesium antacid, a magnesium laxative and a magnesium glycinate capsule are different preparations. The original experiment used magnesium combined with aluminum, so it does not provide a magnesium-only effect or an exact result for glycinate. Preserve the salt and amount when asking about a supplement.
Does this apply to every form of ofloxacin?
This interaction concerns antibiotic taken by mouth and mineral products present in the digestive tract. It does not supply a spacing instruction for ofloxacin eye or ear drops. Ofloxacin is also distinct from levofloxacin, despite the similar names. Check the actual medicine and route before carrying over a recommendation from another prescription.
Evidence and practical considerations
Absorption & effectiveness
Magnesium-containing antacids should be kept at least 2 hours before or after oral ofloxacin, following its current label. A small human study of a combined magnesium/aluminum antacid supports separating doses, but it did not test simultaneous administration or isolate the effect of magnesium alone.
- Exact scope
- magnesium-containing oral antacids, with mixed-product composition retained with oral racemic ofloxacin tablets
- Medication form and route
- oral
- Timing or duration
- Single oral ofloxacin dose with antacid at separated intervals; label precaution applies during co-use.
What remains uncertain
- Combined antacid trial, 16 participants in the relevant arm, no simultaneous-dose arm and no infection outcome. Exact effect cannot be assigned to one mineral or every salt.
Factors that may matter: exact salt and dose; order and interval between oral doses; combination-product ingredients; oral versus nonoral route.
Read the supporting source summaries
Source 1: regulatory product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients prescribed oral ofloxacin tablets.
Product directions require at least 2 hours before or after named mineral products. Ofloxacin can be taken without regard to meals.
How this applies: Exact parent RxCUI 7623, oral racemic ofloxacin. Levofloxacin enantiomer data, ophthalmic products and injections are not substituted. Article-specific counterparty: magnesium-containing oral antacids, with mixed-product composition retained.
Some explanatory wording describes quinolones as a class, but the dosing direction explicitly names ofloxacin. Effect sizes and every supplement salt are not quantified.
Source 2: original human clinical study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: 32 healthy participants in a randomized open-label crossover trial; 16 in each antacid group.
Calcium carbonate had no significant effect at the tested intervals. Magnesium/aluminum antacid 2 hours before produced a small significant reduction in overall exposure and peak. Authors judged effects generally not clinically important with at least 2 hours separation.
How this applies: Direct for the two specified antacids and oral ofloxacin at tested separated intervals. Calcium result cannot clear simultaneous use or every calcium salt. Article-specific counterparty: magnesium-containing oral antacids, with mixed-product composition retained.
Simultaneous administration was not tested. Combined Mg/Al cannot isolate either mineral. Healthy-volunteer pharmacokinetics, not infection outcomes. Full clinical article was not inspected; original author abstract was read.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Exact-drug product guidance and original research checked; complete private article prepared with evidence limitations and current-claim adjudication. | |
| Research summary published |
Article revision: 4f079ba9a7e75edf
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.